7&7 SYNCH

AN OPPORTUNITY FOR YOUR COW HERD?

by Jordan Thomas, Ph.D., University of Missouri state beef reproduction specialist

| INTRODUCTION |

Whether you are striving to raise elite seedstock or highquality commercial calves, a major goal of your operation is— or should be—getting as many cows pregnant as early in the breeding season as possible. Estrus synchronization protocols are a proven tool to do just that. These protocols skew the distribution of when cows conceive during the breeding season, and use of the right protocol can offer the opportunity to carry out an artificial insemination (AI) program in a straightforward manner. What genetics could you access in a straw that you might not otherwise be able to purchase on the hoof?

In our program at the University of Missouri, we have placed a high level of emphasis on research efforts to better control the estrous cycle prior to fixed-time AI. One improved protocol in which we have found great success is the 7 & 7 Synch protocol. In the last year, this protocol has been widely adopted across the United States (and in some locations abroad) as a method to improve conception rates resulting from AI in postpartum beef cows.

Estrus synchronization protocols have been used to facilitate the use of reproductive technologies for decades, so what’s the benefit of a new protocol? When protocols are used to enable use of fixed-time AI or embryo transfer (ET), the goal is to generate a fertile, highly synchronous period of estrus expression among the largest possible proportion of cows. Cows expressing estrus are better candidates for ET and more likely to conceive to AI. Results from extensive evaluation indicate that 7 & 7 Synch achieves this goal, with significant increases in both the proportion of cows expressing estrus and the number becoming pregnant as a result of either AI or ET. With just one additional shot and one additional handling of cows, the increased pregnancy rates achieved with 7 & 7 Synch make it an attractive option for producers in many contexts.

| HOW IT WORKS |

Many protocols for control of the bovine estrous cycle rely upon an initial administration of gonadotropinreleasing hormone (GnRH) to induce ovulation. However, administration of GnRH at a random stage of the estrous cycle only results in ovulation in approximately two-thirds of the cows (sometimes less), as successful induction depends on the presence of a physiologically mature follicle. Since a mature follicle is only present during certain windows of time within the estrous cycle, it is not guaranteed that a cow will ovulate when GnRH is administered. In cases in which ovulation is successfully induced, a new or accessory corpus luteum (CL) is formed and a new ovarian follicular wave is recruited after ovulation. However, when ovulation is not successfully induced, little control is afforded over stage of cycle. That variation among cows’ response ultimately goes on to result in varied timing of onset of estrus and, as a result, varied timing of ovulation.

With 7 & 7 Synch, a simple, single-step approach offers more control over stage of cycle before GnRH administration. At the start of the protocol, a shot of prostaglandin (PG) is given to induce luteolysis, and insertion of a controlled internal drug release (CIDR) device maintains a low level of progesterone, preventing estrus/ovulation as well as atresia of a dominant follicle. This sets up more cows to have a mature follicle present when GnRH is administered, increasing the likelihood of successfully inducing ovulation. From the herd level, greater uniformity in ovarian response among cows leads to a larger proportion of cows expressing estrus in a very narrow window

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(continued from page 42) of time prior to AI. That’s a good thing if performing timed AI or if intending to transfer embryos.

| RESULTS |

Large-scale field trials conducted in our program at the University of Missouri compared use of 7 & 7 Synch to the commonly used 7-Day CO-Synch + CIDR protocol. A collaborative trial with Cross Country Genetics in Westmoreland, Kansas evaluated efficacy in ET recipients on 13 producer operations with over 1,300 postpartum beef cows. With 7 & 7 Synch, 86% of cows expressed estrus following synchronization, compared to the 76% observed with the 7-Day CO-Synch + CIDR. Of those synchronized with 7 & 7 Synch, 40% became pregnant following ET compared to the 34% of the 7-Day CO-Synch + CIDR synchronized cows that became pregnant.

A follow-up trial in our program evaluated field fertility of both sex-sorted and conventional semen for AI of over 1,500 postpartum beef cows in 11 herds across multiple states. Following 7 & 7 Synch, 82% of cows expressed estrus prior to fixed-time AI, compared to 64% of cows following the 7-day CO-Synch + CIDR protocol. It is pretty exciting to see that kind of a heat response prior to fixed-time AI, and pregnancy rates did not disappoint. Pregnancy rates were 72% with conventional semen or 52% with sexed semen following 7 & 7 Synch, compared to 61% with conventional semen and 44% with sexed semen following the 7-day CO-Synch + CIDR protocol.

| FOR SURE |

Thorough published data using 7 & 7 Synch has primarily been collected in postpartum Bos taurus cows. We continue to be cautious about use of this protocol in virgin beef heifers especially. Of course, given the struggles of synchronizing estrus among Bos indicus-influenced cows, we have received a number of questions about use of 7 & 7 Synch in that biological type. Both purebred and composite Bos indicus breeds are more challenging to successfully induce to ovulate in response to GnRH, and it is possible the treatment schedule of the 7 & 7 Synch protocol could address this challenge. Certainly, we are aware of a number of Brangus producers achieving good results with the 7 & 7 Synch currently, but published information is lacking.

A preliminary research effort organized collaboratively by our program at the University of Missouri and Dr. Pedro Fontes’ program at the University of Georgia recently evaluated the ovarian response of Bos indicus¬-influenced cows following 7 & 7 Synch and Bee-Synch II (sometimes called the Bos Indicus PG 5-day + CIDR protocol). Those preliminary evaluations were encouraging, but of course largescale controlled experiments are needed.

For more information on the 7 & 7 Synch protocol, a University of Missouri Extension publication is available online.